1. Field of the Invention
The present invention pertains to flow distributor system for vapor liquid contact towers and, more particularly, to a vapor/liquid distributor for columns incorporating counter-current vapor liquid flow therethrough.
2. History of the Prior Art
It is well known in the prior art to utilize various types of exchange columns in which a gas and a liquid come into contact with one another, preferably in a counter-current flow for purposes of mass or heat transfer, close fractionation and/or separation of feed stock constituents, and other unit operations. Efficient operation requires mass transfer, heat transfer, fluid vaporization and/or condensation, whereby one of the fluids can be cooled with a minimum pressure drop through and in a particular zone or zones of minimum dimensions defining the area and volume thereof. These are prerequisites of efficient operation and are necessary for close fractionation. For this reason counter-current flow of vapor and liquid within such exchange columns have become established methods of such vapor liquid contact in the prior art. The actual vapor liquid interface requires the utilization of a packing bed within the column. Liquid is then distributed atop the packing bed in the most feasible manner while vapor is distributed beneath the packing bed in the lower region of the tower. In this manner liquid trickling downwardly through the packing bed is exposed to the vapor ascending therethrough for vapor liquid contact and interaction. These aspects are more particularly set forth in an article entitled "Packed Column Internals" appearing in the Mar. 5, 1984 edition of Chemical Engineering authored by Dr. Gilbert Chen, one of the inventors herein.
It is well established that the configuration of the packing bed determines the pressure drop, efficiency of the vapor liquid interface and the concomitant mass and energy transfer occurring in a process tower. The means for effective and even distribution of the vapor and the liquid on opposite ends of the packing bed as well as maintenance of that distribution therethrough are critical to an efficient operation. Only with efficient initial vapor and liquid distribution and the maintenance of said distribution throughout the packing bed, will homogenous mixing zones be created therethrough for maximizing the efficiency therein. Efficiency is readily convertible to cost of operation and production quality. For this reason, a myriad of prior art packing designs have been prevalent in conventional exchange columns. The efficiency of the packing is, however, limited to a large extent by the efficiency of the vapor and liquid distribution thereacross For example, failure of either vapor or liquid to evenly distribute over cross-sections of the packing effectively eliminates the utility of the part of the packing where there is poor or no distribution which in turn is directly proportional to the efficiency and cost effectiveness of the operation thereof. Packing bed depths are critical in establishing production criteria and operational costs and failure to evenly distribute vapor liquid and/or maintain homogeniety within the packing bed can lead to serious consequences, particularly in the petroleum refining industry and related areas.
Conventional liquid distributors generally comprise a multi-orifice spray head adapted for dispersing liquid in the form of a spray atop the packing bed. In the utilization of dump packing wherein a plurality of randomly oriented packing elements are disposed within the exchange column, such a liquid distribution technique is sometimes effective. This is true particularly when high efficiency parameters are not of critical significance. However, in the event of high efficiency packing such as that set forth in U.S. Pat. Nos. 4,597,916 and 4,604,247; assigned to the assignee of the present invention, means for homogeneous liquid and gas distribution are of extreme importance. The cost of high density packing of the type set forth in the aforesaid patent applications commands attention to the vapor liquid distribution problem. Even small regions of non-homogenous interaction between said vapor and liquid is an expensive and wasteful loss not consistent with the utilization of high efficiency packing where space and homogeniety in vapor liquid interface is both expected and necessary for proper operation. High efficiency packing of the state of the art varieties as set forth and shown in the aforesaid U.S. patent applications requires counter-current vapor liquid flow through the channels defined by opposed corrugations of sheets disposed therein. If the initial liquid or gas distribution fails to enter a particular corrugation pattern, then precious surface area is lost in the high efficiency packing until the liquid and vapor are urged to migrate into and interact in the unfilled regions of the packing. Only by utilizing proper vapor and liquid distribution means may effective and efficient utilization of high efficiency packing as well as conventional dumped packing be assured.
The development of systems for adequate vapor and liquid distribution in process towers has been limited as set forth above. In the main, it is known to discharge liquid in a more or less patterned spray for adequate liquid distribution and concomitantly to discharge gas in a turbulent configuration to provide adequate vapor distribution. Though generally effective in distributing some vapor and some liquid to most portions of the packing bed, uniform distribution thereacross is generally not obtained without more sophisticated distribution apparatus. For example, unless gas is projected into a myriad of contiguous areas beneath the packing bed with equal pressure existing in each area, the mass flow of vapor upwardly through the packing bed cannot be uniform. Random vapor discharge simply distributes unequal amounts of vapor across the lower regions of the packing bed but does not in any way assure equality in said distribution. Likewise the spray of liquid atop the packing bed though intended to be effective in wetting all surface areas often results in high concentrations of liquid flow in certain packing bed areas, depending on the spray device. Unfortunately, uneven liquid distribution generally occurs in the vicinity of the most even vapor distribution and vice versa. This is because vapor has had a chance to more evenly distribute through the packing bed prior to engaging the liquid distribution flow. It would be an advantage, therefore, to provide means for even liquid and vapor distribution prior to entry of said vapor and liquid into the packing bed and in a manner providing both a uniform spread of said liquid and vapor and a uniform volumetric distribution thereof.
The present invention provides such an improved system of vapor liquid distribution through a sandwiching of two or more relatively thin layers of corrugated, perforated, high efficiency packing, the layers being angularly disposed one to the other. The multi-layer distributor packing is provided in a thin configuration relative to the diameter of the tower and fabricated from a plurality of corrugated sheets angularly inclined one to the other having apertures formed therein for the passage of vapor and/or liquid therethrough. When used in conjunction with a similar high efficiency packing bed, the corrugations of the vapor and/or liquid distributor are equal to and/or larger than the corrugations of the packing bed In this manner pressure drop is not adversely affected through the distributor and the advantages of effective uniform vapor and liquid distribution in a homogeneous flow are obtained. The angular orientation likewise causes sufficient lateral distribution to evenly distribute volumetric flow uniformly across the packing bed for both vapor and liquid interaction and heat and mass transfer Moreover, in this manner similar vapor liquid distributors may be utilized atop the packing bed for distribution of liquid flow, beneath the packing bed for distribution of ascending vapor flow therethrough and/or as part of the packing bed whereby maximum distribution would be achieved prior to engagement of the vapor and/or liquid in the packing bed in accordance with the principles of the present invention.